1. Field of the Invention
The present invention relates to a method for production of an indium tin oxide film which is transparent and conductive and which can be used as a transparent electrode.
2. Description of the Related Art
An indium tin oxide (hereinafter called an ITO) film is transparent when it is conductive. As a result, ITO film shave become indispensable for transparent electrodes for display devices such as liquid crystal and organic electroluminescence display devices or the like, and in other devices. This ITO film can be formed in a polycrystalline state through a process of formation in a high temperature atmosphere using a sputtering method. The resulting polycrystalline ITO film is remarkable as a transparent electrode because of its high transmittance and low resistance.
When the above ITO film is used as an individual pixel electrode of a liquid crystal display device, an organic electroluminescence display device, or the like, it is necessary to etch the formed ITO film to have a pattern of an individual electrode shape.
Meanwhile, there is a great demand that production costs of liquid crystal display devices be reduced, and this, in turn, requires improvement of production efficiency. The production efficiency of the transparent electrode may be improved by shortening an etching time when a patterning is performed.
While the ITO film in the polycrystalline state is excellent as a transparent electrode, it has a low etching rate, and therefore requires a long etching time. Meanwhile, while because the ITO film in the amorphous state has a high etching rate, the etching time can be shortened by adopting it, the amorphous ITO film has disadvantages in its high resistance, low transmittance, and poor properties as an electrode.
To deal with the above disadvantages, it is an object of the present invention to provide a method for efficiently producing an ITO film having low resistance and high transmittance.
In order to achieve the above object, the present invention forms an ITO film at room temperature in a water added atmosphere, and thermally treats the film at about 180xc2x0 C. or more for about one hour or more.
The ITO film formed at room temperature in the wet atmosphere has an amorphous state, so that a desired pattern can be obtained at a high etching rate. And, after the film is formed and patterned, it is thermally treated at a temperature of about 180xc2x0 C. or more (e.g., about 220xc2x0 C.) for about one hour or more (e.g., about one hour to about three hours). The ITO film is polycrystallized, and it becomes possible to lower the film resistance and enhance its transmittance.
According to another embodiment of the present invention, the water added atmosphere in which the ITO film is formed meets a total partial pressure of water of about 8.20xc3x9710xe2x88x923 pascals or less in a film forming chamber. Here, the total partial pressure of water refers to the total of the partial pressure of positively introduced water and the partial pressure of water unintentionally introduced into the film forming chamber.
When the film forming atmosphere for the ITO film is a water added atmosphere, e.g., a total partial pressure of water of 1xc3x9710xe2x88x923 pascals or greater in the film forming chamber, the ITO film can be formed in the amorphous state, and the etching treatment for patterning after forming the film can be performed quickly. Further, it is possible to produce a polycrystalline ITO film having low resistance and high transmittance by thermally treating the ITO film later because the total partial pressure of water in the film forming chamber is suppressed to about 8.20xc3x9710xe2x88x923 pascals or less.
As described above, the present invention can produce an ITO film which can be etched quickly and is remarkable as a transparent conductive film with low resistance and high transmittance.